U.S. patent application number 10/555899 was filed with the patent office on 2007-11-29 for microelectronic substrates with thermally conductive pathways and methods of making same.
This patent application is currently assigned to Merix Corporation. Invention is credited to Benny H. Johnson.
Application Number | 20070272435 10/555899 |
Document ID | / |
Family ID | 38748474 |
Filed Date | 2007-11-29 |
United States Patent
Application |
20070272435 |
Kind Code |
A1 |
Johnson; Benny H. |
November 29, 2007 |
Microelectronic Substrates with Thermally Conductive Pathways and
Methods of Making Same
Abstract
This disclosure suggests microelectronic substrates with
thermally conductive pathways. In one implementation, such a
substrate includes a body and a thermally conductive member. The
Body has a first surface that includes a microelectronic component
mounting site, a second surface separated from the first surface by
a thickness, and an opening extending through at least a portion of
the thickness. The opening is outwardly open at one or both of the
surfaces and has a first portion having a first transverse
dimension and a second portion having a larger second transverse
dimension. The thermally conductive member includes a first
thickness, which is received in the first portion of the opening,
and a second thickness, which is received in the second portion of
the opening. A transverse dimension of the second thickness of the
thermally conductive member is greater than the first transverse
dimension of the opening.
Inventors: |
Johnson; Benny H.; (Aloha,
OR) |
Correspondence
Address: |
PERKINS COIE LLP;PATENT-SEA
P.O. BOX 1247
SEATTLE
WA
98111-1247
US
|
Assignee: |
Merix Corporation
1521 Poplar Lane
Forest Grove
OR
97116
|
Family ID: |
38748474 |
Appl. No.: |
10/555899 |
Filed: |
May 7, 2004 |
PCT Filed: |
May 7, 2004 |
PCT NO: |
PCT/US04/14209 |
371 Date: |
December 4, 2006 |
Current U.S.
Class: |
174/259 ;
257/701 |
Current CPC
Class: |
H05K 2201/10416
20130101; H05K 3/4611 20130101; H05K 2201/09845 20130101; H05K
2201/09309 20130101; H05K 1/0204 20130101; H05K 1/0207
20130101 |
Class at
Publication: |
174/259 ;
257/701 |
International
Class: |
H05K 1/02 20060101
H05K001/02; H05K 7/20 20060101 H05K007/20 |
Claims
1. A microelectronic substrate comprising: a body having a first
surface that includes a microelectronic component mounting site
configured to receive a microelectronic component, a second surface
separated from the first surface by a thickness, and an opening
extending through at least a portion of the thickness and being
outwardly open at one or both of the first and second surfaces, the
opening having a first portion having a first transverse dimension
and a second portion having a larger second transverse dimension; a
thermally conductive member, which has a thermal conductivity
greater than a thermal conductivity of the body, received at least
in part in the opening in the body, the thermally conductive member
having a first thickness received in the first portion of the
opening and a second thickness received in the second portion of
the opening, wherein a transverse dimension of the second thickness
is greater than the first transverse opening dimension.
2. The microelectronic substrate of claim 1 further comprising a
microelectronic component mounted on the mounting site and
electrically coupled to the substrate.
3. The microelectronic substrate of claim 1 wherein the body
includes a patterened electrically conductive layer between the
first and second surfaces.
4. The microelectronic substrate of claim 1 wherein the body
includes a patterened electrically conductive layer between the
first and second surfaces and the electrically conductive layer is
thermally coupled to the thermally conductive member.
5. The microelectronic substrate of claim 1 wherein the body
opening includes a third portion having a third transverse
dimension, the second transverse dimension being larger than the
third transverse dimension and defining a transversely extending
recess between the first and third portions.
6. The microelectronic substrate of claim 5 wherein the second
thickness of the thermally conductive member is received in the
transversely extending recess.
7. The microelectronic substrate of claim 1 wherein the second
thickness of the thermally conductive member comprises a radially
extending flange.
8. The microelectronic substrate of claim 1 wherein the second
thickness of the thermally conductive member -comprises a radially
extending flange that extends about a periphery of the thermally
conductive member.
9. The microelectronic substrate of claim 1 wherein the thermally
conductive member further comprises a third thickness and the
second thickness is disposed between the first and third
thicknesses.
10. The microelectronic substrate of claim 1 wherein the first and
second thickness of the thermally conductive member are integrally
formed.
11. A multi-layer printed circuit board comprising: a first body
layer having a first opening therethrough; a second body layer
juxtaposed with the first body layer and having a second opening
therethrough, the second opening extending outwardly beyond a
periphery of the first opening to define an attachment surface on
the first body layer; an electrically conductive layer disposed
between the first and second body layers; and a thermally
conductive slug received in and extending between the first and
second openings and thermally coupled to the electrically
conductive layer, the slug including a transversely extending
flange that is attached to the attachment surface.
12. The printed circuit board of claim 11 wherein the flange of the
slug is attached to the attachment surface by a thermally
conductive cementitious material.
13. The printed circuit board of claim 11 wherein the slug is
electrically coupled to the electrically conductive layer.
14. The printed circuit board of claim 11 wherein the flange of the
slug is attached to the attachment surface by an electrically
conductive cementitious material that also electrically couples the
slug to the electrically conductive layer.
15. The printed circuit board of claim 11 further comprising a
third body layer juxtaposed with the second body layer and spaced
from the first body layer, the third body layer having a third
opening therethrough that is smaller than the second opening,
wherein the flange of the slug is received between the first and
third body layers.
16. A method of assembling a microelectronic substrate
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/468,801, filed 7 May 2003 and entitled
"LAMINATED THERMAL MANAGEMENT COIN/SLUG FOR PRINTED CIRCUIT
BOARDS," the entirety of which is incorporated herein by
reference.
TECHNICAL FIELD
[0002] This invention generally relates to microelectronic
substrates, e.g., printed circuit boards (PCBs) or the like.
Aspects of the invention are adapted to provide a thermally
conductive pathway through the substrate to help dissipate
heat.
BACKGROUND
[0003] Microelectronic components generate heat in use and can be
damaged if they exceed acceptable operating temperatures. As
high-energy microelectronic components become more prevalent and
powerful, the thermal load produced by these components becomes
increasingly difficult to dissipate from the system.
[0004] Microelectronic components are commonly attached to a
substrate such as a printed circuit board (PCB) to form a larger
microelectronic component assembly. A single microelectronic
component assembly will often have numerous microelectronic
components, each of which generates heat in use, mounted on a
single PCB. Dissipation of heat from the side of the PCB bearing
the microelectronic components has been and continues to be a
significant problem for PCB designers.
[0005] A variety of approaches are used in the art to dissipate
heat generated by microelectronic components. One solution employs
surface-mounted thermal risers with prongs or fins to dissipate
heat to the air adjacent the PCB. Other approaches use arrays of
copper plated holes (vias) that conduct the thermal load through
the PCB and thence to a thermal mass, e.g., a chassis or housing
for the microelectronic component assembly or a secondary heat sink
on the back side of the finished assembly. One of the most
effective thermal management devices is the use of a metal coin or
slug to conduct the thermal load through the circuit board to such
a thermal mass. After the PCB is formed, e.g., by laminating
multiple layers together, a through-opening or cavity may be
machined through the thickness of the PCB, forming a passage
between the component side and the back side of the PCB. Coins or
slugs are then mounted in the opening or cavity using thermal
grease or solder, typically as part of the component assembly
process during which microelectronic components are mounted on the
PCB.
[0006] The following patents, the entirety of each of which is
incorporated herein by reference, generally relate to PCB thermal
management features:
[0007] U.S. Pat. No. 5,779,134--Method for surface mounting a heat
sink to a printed circuit board
[0008] U.S. Pat. No. 6,411,516--Copper slug pedestal for a printed
circuit board
[0009] U.S. Pat. No. 6,190,941--Method of fabricating a circuit
arrangement with thermal vias
[0010] U.S. Pat. No. 6,200,407--Method of making a multilayer
circuit board having a window exposing an enhanced conductive layer
for use as an insulated mounting area.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic perspective view of a microelectronic
component assembly in accordance with one embodiment.
[0012] FIG. 2 is a schematic cross-sectional view of the
microelectronic component substrate of FIG. 1, taken along line
2-2.
[0013] FIG. 3 is a schematic 3-D exploded cut-away view of a
portion of the microelectronic component substrate of FIGS. 1 and
2.
[0014] FIG. 4 is a schematic 3-D laminated cut-away view of the
portion of the microelectronic component substrate shown in FIG.
3.
[0015] FIG. 5 is a schematic 3-D laminated close-up cut-away view
of a portion of the microelectronic component substrate of FIG.
4.
[0016] FIG. 6 is a schematic cross-sectional view of a portion of a
microelectronic component substrate in accordance with another
embodiment.
[0017] FIG. 7 is a schematic cross-sectional view of a portion of a
microelectronic component substrate in accordance with yet another
embodiment.
DETAILED DESCRIPTION
A. Overview
[0018] Various embodiments of the present invention provide
microelectronic component assemblies and methods of manufacturing
microelectronic component assemblies. The term "microelectronic
component" may encompass a variety of articles of manufacture,
including memory modules (e.g., SIMM, DIMM, DRAM, flash-memory),
ASICs, processors, semiconductor wafers, semiconductor dies
singulated from such wafers, or any of a variety of other types of
microelectronic devices or components therefor. As used herein,
"microelectronic component assembly" refers to at least one
microelectronic component operatively coupled to a microelectronic
component substrate and may include any number of microelectronic
components or other structures, e.g., fin-bearing heat sinks. The
more general term "microelectronic component" encompasses within
its scope microelectronic component assemblies.
[0019] For ease of understanding, the following discussion is
broken down into two areas of emphasis. The first section describes
aspects of microelectronic component assemblies in certain
embodiments of the invention. The second section outlines methods
of manufacturing microelectronic component assemblies in accordance
with other embodiments of the invention.
B. Microelectronic Component Assemblies
[0020] FIG. 1 schematically illustrates a microelectronic component
assembly 10 that generally includes a microelectronic substrate 20
that carries a number of microelectronic components 12. Each of the
microelectronic components 12 may be mounted at a mounting site 14
(shown schematically in dashed lines) that is adapted to receive
the particular microelectronic component 12 for mechanical and
electrical connection to the microelectronic substrate 20. Any of a
variety of known microelectronic components 12 may be attached to
the microelectronic component substrate 30 in any manner known in
the art.
[0021] The microelectronic component substrate 20 includes a body
25 that carries a thermally conductive member 100. The body 25 has
a "front" surface 22 and a "back" surface 24 spaced apart from one
another by a thickness T of the body 25. (Reference to "front" and
"back" is solely for purposes of convenience and does not imply any
particular orientation of the microelectronic component substrate
20.) A periphery 26 of the body 25 extends between the front and
back surfaces 22 and 24. In the illustrated embodiment, the
periphery 26 carries an electrical interface 28 to enable coupling
of the microelectronic component assembly 10 to other
microelectronic components (not shown), e.g., a bus of a computer
that communicates with a series of other microelectronic component
assemblies.
[0022] FIGS. 2-5 illustrate the microelectronic component substrate
20 of FIG. 1 in greater detail. As shown in these drawings, the
body 25 of this particular microelectronic component substrate 20
comprises a plurality of separate body layers that together define
the overall thickness T of the body 25. In particular, the body 25
of FIGS. 2-5 includes a "front" body layer 30, a "back" body layer
40, and an intermediate body layer 50 disposed between the front
and back body layers 30 and 40. In this arrangement, an inner
surface 32 of the front body layer 30 is juxtaposed with a front
surface 52 of the intermediate body layer 50. Likewise, an inner
surface 42 of the back body 40 is juxtaposed with a back surface 54
of the intermediate body layer 50.
[0023] At least one of the body members 30, 40, and 50 may carry an
electrically conductive layer 55 to which some or all of the
microelectronic components 12 (FIG. 1) are electrically coupled. As
is known in the art, such an electrically conductive layer 55
typically comprises a metal layer that has been patterned to define
an electrical circuit that interconnects the microelectronic
components 12 to provide a functioning microelectronic component
assembly 10. In the illustrated embodiment, the intermediate body
layer 50 includes a first electrically conductive layer 55a on the
front surface 52 and a second electrically conductive layer 55b on
the back surface 54. In one embodiment, one of these electrically
conductive layers 55 may function as a ground layer for the
microelectronic component assembly 10.
[0024] Each of the body layers 30, 40, and 50 may comprise any of a
variety of dielectric materials. For example, the body layers 30,
40, and 50 may comprise a relatively thin, flexible film to provide
a flexible printed circuit. In other embodiments, the body layers
30, 40, and 50 may comprise a more rigid dielectric material, e.g.,
any material commonly employed in PCBs. In select embodiments, each
of the layers 30, 40, and 50 may comprise a glass filament- and
particulate-reinforced resins such as FR4, High TG FR4, or high
performance RF materials. The material of body layers 30, 40, and
50 may be selected to achieve a particular electrical or thermal
performance objective of the finished microelectronic component
assembly 10. In the illustrated embodiment, each of the body layers
30, 40, and 50 are formed of the same material. In other
embodiments, the layers 30, 40, and 50 may be different from one
another.
[0025] As is known in the art, the body layers 30, 40, and 50 may
be laminated together using an adhesive dr other cementitious
material. In FIGS. 2-5, a first adhesive layer 60a attaches the
front body layer 30 to the intermediate body layer 50 and a second
adhesive layer 60b attaches the back body layer 40 to the
intermediate body layer 50. A wide variety of suitable adhesives
are known in the art. If the body layers 30, 40, and 50 comprise
FR4, any of a variety of commercially available FR4 adhesive
materials may be used. In the embodiment shown in FIG. 3, the
adhesive layers 60a and 60b comprise a sheet that is
pre-impregnated with a suitable adhesive resin.
[0026] The front body layer 30 includes a first opening 36 that
extends therethrough, the intermediate body layer 50 includes a
second opening 56 that extends through its thickness, and the back
layer 40 includes a third opening 46 therethrough. The second
opening 56 extends outwardly beyond a periphery of at least one of
the first and third openings 36 and 46. In the illustrated
embodiment, the first and third openings 36 and 46 are about the
same size and the second opening 56 extends outwardly beyond the
periphery of both of those openings. As a consequence, a transverse
recess is formed between the front and back body layers 30 and
40.
[0027] This leaves a peripheral surface of the inner surface 32
juxtaposed with, but spaced from, a peripheral portion of the inner
surface 42 of the back body layer 40.
[0028] The openings may be precisely machined using a CNC router or
the like to create concentric openings to accommodate the thermally
conductive members 100. The lamination adhesive layers 60 may be
laser or die-cut to produce openings that match openings 36 and
46.
[0029] As noted above, the microelectronic substrate 20 includes
one or more thermally conductive members or "slugs" 100, with two
such thermally conductive members 100 being shown in the
microelectronic component assembly 10 of FIG. 1. The slugs 100 may
comprise an integrally formed and suitably shaped piece of metal or
other material that is more thermally conductive than the body 25.
A polymeric material can be used as the thermally conductive member
100, in many embodiments the thermally conductive member 100 is a
thermally conductive metal, e.g., copper or aluminum. If the slug
100 is to be electrically coupled to the conductive layers 55,
copper and aluminum would meet that objective, as well.
[0030] The slug 100 includes a front thickness adjacent its front
surface 102, a back thickness adjacent its back surface 104 and an
intermediate thickness disposed between the front and back
thicknesses. The intermediate thickness has a lateral dimension
that is greater than the corresponding dimension of one or both of
the front and back thicknesses. As a consequence, the slug 100
includes a transversely extending flange 110 that extends
transversely outwardly into the recess between the front and back
body members 30 and 40 of the body 25. The flange may define a
shoulder that can be juxtaposed with and bonded to an attachment
surface of each of the front and back body members 30 and 40 by
means of a suitable adhesive 70. In the illustrated embodiment, the
first attachment adhesive 70a may attach the flange 110 to the
inner surface 32 of the front body member 30 and a second
attachment adhesive 70b may attach the flange 110 to the inner
surface 42 of the back body layer 40. These attachment adhesives 70
may be screen-printed or pre-formed. The adhesive may be thermally
conductive and/or electrically conductive. If the adhesive 70 is
electrically conductive, it can couple the slug to conductive
layers 55 of the body 25.
[0031] By carefully specifying the thickness of the slug 100 to
match the thickness of the body, good planarity with slight
prominence of the slug 100 can be achieved. In some embodiments,
slight prominence of the slug 100 may be desirable to provide good
contact with a microelectronic component 12 while not
over-stressing the component leads. In one exemplary design, the
thickness of the coin can be slightly thicker than the thickness T
of the body 25.
[0032] In an embodiment where no electrical ground properties are
required between the slug and the ground plane of the PCB, the
flange 110 can be eliminated completely. Without a flange 110,
assembly can be even easier and less expensive.
[0033] FIGS. 6 and 7 illustrate alternative designs with
differently shaped slugs 100a and 100b. In FIG. 6, the flange 110a
is adjacent an end of the slug 100 but is recessed inside the back
body layer. The substrate of FIG. 7 includes more body layers, but
the design and construction may otherwise parallel that discussed
above. The flange may be located on either side (FIG. 6) of the
slug 100, in the center (FIG. 2-5) or off-center (FIG. 7).
[0034] FIG. 5 illustrates an alternative cross-sectional design
that can be built in accordance with another embodiment of the
invention. This process of laminating the coin/slug (1) directly in
the PCB does not require and is not limited to the center located
"flanged" detail. Other coin/slug designs including those
illustrated and others which are not specifically depicted, may be
suitable for use, too. FIG. 5 shows a flange located on one side of
the coin/slug (1) and one layer of conductive adhesive material (4)
providing ground connection to only one layer in the multilayer
PCB. The rest of the PCB may comprise a standard design copper clad
core material (2), and lamination adhesive material (3).
C. Methods of Manufacture
[0035] The exploded, 3-D cut-away view of FIG. 3 schematically
illustrates the relationship between the various components of the
microelectronic component substrate 20 during manufacture. This
view also suggests the sequence of assembly steps that are required
to assemble the substrate 20.
[0036] The components of the substrate 20 may be assembled,
referred to as a "collation lay-up," of the specific
microelectronic component assembly of FIG. 2 may follow the
following sequence:
[0037] 1. Back layer 40
[0038] 2. Conductive adhesive material 70b
[0039] 3. Slug 100
[0040] 4. Lamination adhesive material 60b
[0041] 5. Intermediate body layer 50
[0042] 6. Lamination adhesive material 60a
[0043] 7. Conductive adhesive material 70a
[0044] 8. Front layer 30
[0045] This arrangement facilitates easy assembly of the
microelectronic component substrate 20 and securely integrates the
slug 100 in the structure for better mechanical and thermal
connection.
[0046] Some advantages of select embodiments include: [0047] a. By
manufacturing PCB dielectric materials with concentric features
allowing the coin/slug to be sized and toleranced to nest in the
openings; [0048] b. By manufacturing PCB compatible adhesive
materials that align with the laminate features and coin/slug,
which can facilitate assembly in conventional lamination presses;
and/or [0049] c. Selecting any of various cross-section coin/slug
designs, e.g., designs having offset flanges or centerline flanges
aligning with one or more layers in the PCB construction. Such a
flange could be circumferential or limited to specific locations
around the coin creating isolated protrusions.
[0050] The above-detailed embodiments of the invention are not
intended to be exhaustive or to limit the invention to the precise
form disclosed above. Specific embodiments of, and examples for,
the invention are described above for illustrative purposes, but
those skilled in the relevant art will recognize that various
equivalent modifications are possible within the scope of the
invention. For example, whereas steps are presented in a given
order, alternative embodiments may perform steps in a different
order. The various embodiments described herein can be combined to
provide further embodiments.
[0051] Unless the context clearly requires otherwise, the words
"comprise," "comprising," and the like are to be construed in an
inclusive sense as opposed to an exclusive or exhaustive sense,
i.e., in a sense of "including, but not limited to." In general,
the terms used in this disclosure should not be construed to limit
the invention to the specific embodiments described above unless
the above-detailed description explicitly defines such terms. While
certain aspects of the invention are presented above in certain
exemplary embodiments, the inventors contemplate various aspects of
the invention in any number of embodiments. The inventors reserve
the right to add additional claims after filing the application to
pursue additional claim forms for aspects of the invention not
currently claimed.
* * * * *